Field of the Invention
The present invention relates to a valve mechanism for a high pressure tank and a valve device for a high pressure tank.
Discussion of the Background
In a high pressure tank to be used for a fuel cell powered vehicle and a stationary fuel cell, high pressure hydrogen of several dozens of MPa is stored. Therefore, the high pressure is applied also to a piping system connecting to the high pressure tank. When assembling the fuel cell powered vehicle or at the time of maintenance, the so-called airtightness inspection is carried out in order for confirming whether or not there is any leakage in the piping system. Concretely, high pressure fluid is filled into the piping system, and presence or absence of the leakage of the fluid from the piping system is inspected.
At the time of inspection, the hydrogen and the like as fuel is not used, inert gas such as helium and the like is used. In the airtightness inspection, a valve device (manual valve) for airtightness inspection is required to be fitted in the high pressure tank so as not to allow the inert gas to enter the high pressure tank. As the valve device for the airtightness inspection there is a manual safety restraint valve as disclosed in a Japanese Patent Application Laid-Open Publication No. H07-301359. This manual safety restraint valve is arranged in a gas flow passage. A threaded stem is rotated so as to tighten a resilient gasket against a second valve seat.